Chip package with asymmetric molding

ABSTRACT

A chip package with asymmetric molding including a lead frame, a chip, an adhesive layer, bonding wires and an encapsulant, is provided. The lead frame includes a frame body and at least a turbulent plate. The frame body has inner lead portions and outer lead portions. The turbulent plate is bended upwards to form a bulge portion and the first end of the turbulent plate is connected to the frame body. The chip is fixed under the inner lead portions and the turbulent plate is located at one side of the chip. The adhesive layer is disposed between the chip and the inner lead portions, and the bonding wires are electrically connected between the chip and the corresponding inner lead portions, respectively. The encapsulant encapsulates at least the chip, the bonding wires, the inner lead portions, the adhesive layer and the turbulent plate.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan applicationserial no. 94125376, filed on Jul. 27, 2005. All disclosure of theTaiwan application is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a chip package with asymmetric molding,and particularly to a chip package with a lead frame.

2. Description of the Related Art

For a dynamic random access memory (DRAM), the packaging method can becategorized into small outline J-lead (SOJ) package and thin smalloutline package (TSOP), both of which has the advantage of fasttransmission rate, good heat dispersion and compact size. In terms oflead frames, the SOJ package and the TSOP can further be classified intolead on chip (LOC) package, U.S. Pat. No. 4,862,245, and chip on lead(COL) package, U.S. Pat. No. 4,989,068.

FIG. 1A is a schematic cross-sectional view of a conventional thin smalloutline package TSOP having lead on chip (LOC) configuration. Referringto FIG. 1A, a conventional thin small outline package (SOP) 100 aincludes a lead frame 110, a chip 120, an adhesive layer 130, firstbonding wires 140 a and an encapsulant 150, wherein the lead frame 110has inner lead portions 112 and outer lead portions 114.

The chip 120 is fixed on the lower surfaces of inner lead portionsthrough the adhesive layer 130 between the chip 120 and the inner leadportion 112. The first bonding wires 140 a are electrically connectedbetween the chip 120 and the corresponding inner lead portions 112,respectively. The encapsulant 150 is used for encapsulating the innerlead portions 112, the chip 120, the adhesive layer 130 and the firstbonding wires 140 a. Note that the thickness D1 of the encapsulant 150over the outer lead portions 114 is 1:3 in proportion to the thicknessD2 of the encapsulant 150 under the outer lead portions 114. Therefore,as the encapsulant 150 condenses and shrinks, the TSOP 100 a can bedamage due to the warpage.

FIG. 1B is a schematic cross-sectional view of another conventional thinsmall outline package (TSOP) with lead on chip (LOC) configuration. FIG.1B is similar to FIG. 1A. The difference in FIG. 1B is the conventionalTSOP 100 b herein further includes second bonding wires 140 b and thelead frame 110 further includes bus bars 116, which are adjacent to theinner lead portions 112. In addition, the second bonding wires 140 b areelectrically connected between the bus bars 116 and the chip 120.However, the conventional TSOP 100 b still has the above-describedproblems.

SUMMARY OF THE INVENTION

Based on the above, an object of the present invention is to provide achip package with asymmetric molding having better reliability.

Another object of the present invention is to provide a chip packagewith asymmetric molding, for reducing the warpage caused when theencapsulant condenses and shrinks.

Based on the above and other objects, the present invention provides achip package with asymmetric molding, which includes a lead frame, achip, an adhesive layer, first bonding wires and an encapsulant, whereinthe lead frame includes a frame body and at least a turbulent plate. Theframe body has inner lead portions and outer lead portions. Theturbulent plate bends upwards to form a bulge portion and has a firstend and a second end, wherein the first end is connected to the framebody. The chip is fixed on the lower surfaces of inner lead portionsthrough the adhesive layer between the chip and the inner lead portions.The turbulent plate is located at one side of the chip. The firstbonding wires are electrically connected between the chip and thecorresponding inner lead portions, respectively. The encapsulant is usedfor encapsulating at least the chip, the first bonding wires, the innerlead portions, the adhesive layer and the turbulent plate. Wherein, thethickness of the encapsulant part under the outer lead portions and thethickness of the encapsulant part over the outer lead portions are notequal.

Based on the above and other objects, the present invention provides achip package with asymmetric molding, which includes a lead frame, achip, an adhesive layer, first bonding wires and an encapsulant, whereinthe lead frame includes a frame body and at least a turbulent plate. Theframe body has inner lead portions, outer lead portions and a die pad.The turbulent plate bends upwards to form a bulge portion and has afirst end and a second end, wherein the first end is connected to theframe body. The chip is fixed on the die pad. The turbulent plate islocated at one side of the chip. The adhesive layer is disposed betweenthe chip and the die pad and the first bonding wires are electricallyconnected between the chip and the corresponding inner lead portions,respectively. The encapsulant is used for encapsulating at least thechip, the first bonding wires, the inner lead portions, the adhesivelayer, the turbulent plate and the die pad. Wherein, the thickness ofthe encapsulant part under the outer lead portions and the thickness ofthe encapsulant part over the outer lead portions are not equal.

According to the embodiment of the present invention, the second end ofthe turbulent plate can be bended to be flat.

According to the embodiment of the present invention, the turbulentplate is bended upwards to form a bulge portion first, then bendeddownwards and the second end thereof is higher than the inner leadportions.

According to the embodiment of the present invention, the turbulentplate is bended upwards to form a bulge portion first, then bendeddownwards and the second end of the turbulent plate and the inner leadportions are coplanar.

According to the embodiment of the present invention, the turbulentplate is bended upwards to form a bulge portion first, then bendeddownwards and the second end of the turbulent plate is lower than theinner lead portions.

According to the embodiment of the present invention, the lead framefurther includes at least a supporting bar connected between the secondend of the turbulent plate and the frame body. Alternatively, thesupporting bar can be connected between the frame body and the turbulentplate.

According to the embodiment of the present invention, the inner leadportions can be designed as down-set.

According to the embodiment of the present invention, the die pad can belower than the inner lead portions.

According to the embodiment of the present invention, the frame body canfurther include bus bars, which are adjacent to the inner lead portions.In addition, the chip package with asymmetric molding further includessecond bonding wires electrically connected between the chip and thecorresponded bus bars, respectively. The encapsulant furtherencapsulates the second bonding wires and the bus bars.

According to the embodiment of the present invention, the turbulentplate can have openings.

According to the embodiment of the present invention, the thickness ofthe encapsulant part under the bulge portion of the turbulent plate andthe thickness of the encapsulant part over the bulge portion of theturbulent plate are not equal.

Based on the above described, the present invention adds a novelturbulent bended upwards to prevent the warpage caused when theencapsulant condenses and shrinks, thus enhancing the reliability of thechip package.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve for explaining theprinciples of the invention.

FIG. 1A is a schematic cross-sectional view of a conventional thin smalloutline package (TSOP) with lead on chip (LOC) configuration.

FIG. 1B is a schematic cross-sectional view of another conventional thinsmall outline package (TSOP) with lead on chip (LOC) configuration.

FIG. 2A is a schematic top view of a chip package before encapsulationaccording to the first embodiment of the present invention, wherein thefirst bonding wire and the encapsulant are not shown.

FIG. 2B is a schematic cross-sectional view along plane A-A′ of the chippackage after encapsulation in FIG. 2A.

FIG. 2C is a schematic cross-sectional view along plane B-B′ of the chippackage after encapsulation in FIG. 2A.

FIG. 3A is a schematic top view of a chip package before encapsulationaccording to the second embodiment of the present invention, wherein thefirst bonding wires, the second bonding wires and the encapsulant arenot shown.

FIG. 3B is a schematic cross-sectional view along plane A-A′ of the chippackage after encapsulation in FIG. 3A.

FIG. 3C is a schematic cross-sectional view along plane B-B′ of the chippackage after encapsulation in FIG. 3A.

FIG. 3D is a schematic cross-sectional view of another chip package withasymmetric molding according to the first embodiment of the presentinvention.

FIGS. 4A-4D are schematic cross-sectional views of a chip packageaccording to the third embodiment of the present invention.

DESCRIPTION OF THE EMBODIMENTS The First Embodiment

FIG. 2A is a schematic top view of a chip package before encapsulationaccording to the first embodiment of the present invention, wherein thefirst bonding wire and the encapsulant are not shown. FIG. 2B is aschematic cross-sectional view along plane A-A′ of the chip packageafter encapsulation in FIG. 2A, and FIG. 2C is a schematiccross-sectional view along plane B-B′ of the chip package afterencapsulation in FIG. 2A. Referring to FIGS. 2A and 2B, the chip packageof the embodiment includes a lead frame 210, a chip 220, an adhesivelayer 230, bonding wires 240 a and an encapsulant 250, wherein the chip220 is fixed under the lead frame 210, the adhesive layer 230 isdisposed between the chip 220 and the lead frame 210 for fixing the chip220. The material of the adhesive layer 230 can be polyimide ornonconductive glue. The first bonding wires 240 a are electricallyconnected between the chip 220 and the lead frame 210 and the materialof the first bonding wires 240 a can be gold, aluminum or otherconductive materials. The encapsulant 250 is used for encapsulating thepartial lead frame 210, the chip 220, the adhesive layer 230 and thefirst bonding wires 240 a and the material of the encapsulant 250 can beepoxy or other insulation materials.

Referring to FIGS. 2A and 2C, in more detail, the lead frame 210includes a frame body 212 and at least a turbulent plate 214, whereinthe material of the lead frame 210 can be iron, copper or other metal.Besides, the frame body 212 has inner lead portions 212 a and outer leadportions 212 b. The turbulent plate 214 has a first end 214 a and asecond end 214 b, wherein the first end 214 a is connected to the framebody 212. The turbulent plate 214 is bended upwards to form a bulge. Thesecond end 214 b of the turbulent plate 214 is higher than the innerlead portions 212 a. In addition, the second end 214 b can be bended tobe flat or in other angles.

The turbulent plate 214 of the lead frame 210 resides at both sides ofthe long-axis of the chip 220. However, the present invention doesn'tlimit the quantity of the turbulent plate 214 and the location thereof.In the embodiment, the lead frame 210 can further include a supportingbar 216 connected between the second end 214 b of the turbulent plate214 and the frame body 212. In other words, both ends of the turbulentplate 214 can be connected to the frame body 212. The supporting bar 216can be alternatively connected between the frame body 212 and the sideedge of the turbulent plate 214. Alternatively, the second end 214 b ofthe turbulent plate 214 is not connected to the frame body 212.Similarly, the present invention doesn't limit the quantity of thesupporting bar 216 and the location thereof. In addition, to improvemold flow, the turbulent plate 214 can have openings 214 c.

In the embodiment, there is no height difference between the inner leadportions 212 a and the frame body 212, while in another embodiment, theinner lead portions 212 a can be designed as down-set. That is, theinner lead portions 212 a can be disposed lower than the frame body 212.The adhesive layer 230 is disposed between the chip 220 and the innerlead portions 212 a, while the first bonding wires 240 a areelectrically between the inner lead portions 212 a and the chip 220.

Note that the thickness D3 of the encapsulant part 250 over the outerlead portions 212 b and the thickness D4 of the encapsulant part 250under the outer lead portions 212 b are not equal. In other words, thechip package of the embodiment applies asymmetric molding. In addition,the thickness D6 of the encapsulant part 250 under the bulge portion 214d of the turbulent plate 214 and the thickness D5 of the encapsulantpart 250 over the bulge portion 214 d are not equal.

With a different material of the lead frame 210, the stress distributionand warpage of whole chip package produced as the encapsulant 250condenses and shrinks are not identical. The design of the turbulentplate 214 could improve the stress distribution and warpage of wholechip package as the encapsulant 250 condenses and shrinks. Therefore,the present invention provides a chip package with higher reliabilitythan the prior art. Besides, the present invention doesn't limit theapplications to lead on chip package. In fact, the present invention canbe applied to any chip packages having a die pad configuration, which isdescribed in the following.

The Second Embodiment

FIG. 3A is a schematic top view of a chip package before encapsulationaccording to the second embodiment of the present invention, wherein thefirst bonding wires, the second bonding wires and the encapsulant arenot shown. FIG. 3B is a schematic cross-sectional view along plane A-A′of the chip package after encapsulation in FIG. 3A and FIG. 3C is aschematic cross-sectional view along plane B-B′ of the chip packageafter encapsulation in FIG. 3A. Referring to FIGS. 3A-3C, the embodimentis similar to the first embodiment. The difference of the embodiment isthat the turbulent plate 314 has a first end 314 a and a second end 314b and the first end 314 a is connected to the frame body 212. Theturbulent plate 314 is bended upwards to form a bulge portion 314 d,then bended downwards. The second end 314 b and the inner lead portions212 a are coplanar. However, the second end 314 b can also be bended tobe flat or in other angles. Like the first embodiment, the second end314 b of the turbulent plate 314 can also be connected to the frame body212 (not shown) via the supporting bar 216; or, the second end 314 b ofthe turbulent plate 314 can be a free end. The supporting bar 216 canalso be connected between the side edge of the turbulent plate 314 andthe frame body 212. The turbulent plate 314 can also have a plurality ofopenings 314 c.

In the same way, the thickness D6 of the encapsulant part 250 under thebulge portion 314 d of the turbulent plate 314 and the thickness D5 ofthe encapsulant part 250 over the bulge portion 314 d of the turbulent314 are not equal.

Referring to FIGS. 3A and 3B, the frame body 210 of the embodimentfurther includes bus bars 218, which are adjacent to the inner leadportions 212 a. The chip package having an asymmetric molding of theembodiment further includes second bonding wires 240 b connected betweenthe chip 220 and the corresponding bus bars 218, respectively. In fact,the bus bars 218 of the embodiment can be applied to the firstembodiment. Besides, in the embodiment, the second end 314 b of theturbulent plate 314 and the inner lead portions 212 a are notnecessarily coplanar, which will be described hereafter.

FIG. 3D is a schematic cross-sectional view of another chip package withasymmetric molding according to the first embodiment of the presentinvention. Referring to FIG. 3D, the second end 314 b of the turbulentplate 314 can also be bended to be lower than the inner lead portions212 a. However, the second end 314 b can also be bended to be flat or inother angles. Similarly, the second end 314 b of the turbulent plate 314can be a free end; or, the second end 314 b of the turbulent plate 314can be connected to the frame body 212 via a supporting bar 216. Thesupporting bar 216 can also be connected between the turbulent plate 314and the frame body 212.

The Third Embodiment

FIGS. 4A-4D are schematic cross-sectional views of a chip packageaccording to the third embodiment of the present invention. Referring toFIGS. 4A and 4B, the chip package of the embodiment includes a leadframe (not shown), a chip 420, an adhesive layer 430, first bondingwires 440 a and an encapsulant 450, wherein the lead frame includes aframe body 412 and at least a turbulent plate 414. The frame body 412has inner lead portions 412 a, outer lead portions 412 b and a die pad412 c. The chip 420 is disposed on the die pad 412 c, while the adhesivelayer 430 is disposed between the chip 420 and the die pad 412 c forfixing the chip 420. The first bonding wires 440 a are electricallyconnected between the chip 420 and the inner lead portions 412 a. Theencapsulant 450 encapsulates at least the chip 420, the first bondingwires 440 a, the inner lead portions 412 a, the adhesive layer 430, theturbulent plate 414 and the die pad 412 c, wherein the thickness D4 ofthe encapsulant part 450 under the outer lead portions 412 b and thethickness D3 of the encapsulant part 450 over the outer lead portions412 b are not equal.

As the above-described embodiment, the turbulent plate 414 has a firstend 414 a and a second end 414 b and the first end 414 a is connected tothe frame body 412. The turbulent plate 414 is bended upwards to form abulge portion 414 c and the second end 414 b is located over the innerlead portions 412 a. In addition, the second end 414 b can be bended tobe flat or in other angles. The lead frame 410 can further include asupporting bar (similar to the one shown in FIG. 2A and FIG. 3A)connected between the second end 414 b of the turbulent plate 414 andthe frame body 412. The supporting bar can be alternatively connectedbetween the frame body 412 and the side edge of the turbulent plate 414.Alternatively, the second end 414 b of the turbulent plate 414 is notconnected to the frame body 412. In addition, the turbulent plate 414can also have openings (similar to the ones shown in FIG. 2A and FIG.3A). Note that the thickness D6 of the encapsulant part 450 under thebulge portion 412 c of the turbulent plate 414 and the thickness D5 ofthe encapsulant part 450 over the bulge portion 412 c of the turbulentplate 414 are not equal.

In the embodiment the frame body 410 further includes bus bars 418,which are adjacent to the inner lead portions 412 a. The chip packagewith asymmetric molding of the embodiment further includes secondbonding wires 440 b connected between the chip 420 and the correspondingbus bars 418, respectively. The inner lead portions 412 a can bedesigned as down-set and the die pad 412 c can also be lower than theinner lead portions 412 a.

Referring to FIG. 4C, the turbulent plate 414 also can be bended upwardsto form a bulge portion 414 c, then bended downwards and the second end414 b and the inner lead portions 412 a are on a same plane. However,the second end 414 b of FIG. 4C can also be bended to be flat or inother angles. As the above-described embodiment, the second end 414 b ofthe turbulent plate 414 can also be connected to the frame body 412 viaa supporting bar (similar to the one shown in FIG. 2A). Alternatively,the second end 414 b of the turbulent plate 414 can be a free end andthe supporting bar can be connected between the side edge of theturbulent plate 414 and the frame body 412. In addition, the turbulentplate 414 can have a plurality of openings (similar to the one shown inFIG. 2A). Similarly, the thickness D6 of the encapsulant part 450 underthe bulge portion 414 c of the turbulent plate 414 and the thickness D5of the encapsulant part 450 over the bulge portion 414 c of theturbulent plate 414 are not equal.

Referring to FIG. 4D, the turbulent plate 414 can also be bended upwardsto form a bulge portion 414 c, then bended downwards and the second end414 b of the turbulent plate 414 is lower than the inner lead portions412 a. The second end 414 b in FIG. 4D can also be bended to be flat orin other angles. In the same way, the second end 414 b of the turbulentplate 414 can be a free end. Alternatively, the second end 414 b of theturbulent plate 414 can also be connected to the frame body 412 via asupporting bar, and the supporting bar can be connected between the sideedge of the turbulent plate 414 and the frame body 412.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the specification andexamples to be considered as exemplary only, with a true scope andspirit of the invention being indicated by the following claims andtheir equivalents.

1. A chip package with asymmetric molding, comprising: a lead frame,comprising: a frame body, having a plurality of inner lead portions, aplurality of outer lead portions and a die pad, wherein the die pad islower than the inner lead portions; at least a turbulent plate having afirst end and a second end, wherein the turbulent plate is bendedupwards at a first bending point and then bended at a second bendingpoint to form a bulge portion, and the first end is connected to theframe body; a chip, fixed on the die pad, wherein the turbulent plate islocated at a side of the chip; an adhesive layer, disposed between thechip and the die pad; a plurality of first bonding wires, electricallyconnected between the chip and the corresponding inner lead portions,respectively; and an encapsulant, encapsulating at least the chip, thefirst bonding wires, the inner lead portions, the adhesive layer, theturbulent plate and the die pad, wherein the thickness of theencapsulant part under the outer lead portions and the thickness of theencapsulant part over the outer lead portions are not equal.
 2. The chippackage with asymmetric molding as recited in claim 1, wherein thesecond end of the turbulent plate is bended to be flat.
 3. The chippackage with asymmetric molding as recited in claim 2, wherein thesecond end of the turbulent plate is higher than the inner leadportions.
 4. The chip package with asymmetric molding as recited inclaim 1, wherein the turbulent plate is bended upwards to form the bulgeportion, then bended downwards and the second end of the turbulent plateis higher than the inner lead portions.
 5. The chip package withasymmetric molding as recited in claim 1, wherein the turbulent plate isbended upwards to form the bulge portion, then bended downwards, and thesecond end of the turbulent plate and the inner lead portions arecoplanar.
 6. The chip package with asymmetric molding as recited inclaim 1, wherein the turbulent plate is bended upwards to form the bulgeportion, then bended downwards and the second end of the turbulent plateis lower than the inner lead portions.
 7. The chip package withasymmetric molding as recited in claim 1, wherein the lead frame furthercomprises at least a supporting bar connected between the second end ofthe turbulent plate and the frame body.
 8. The chip package withasymmetric molding as recited in claim 1, wherein the lead frame furthercomprises at least a supporting bar connected between the frame body anda side edge of the turbulent plate.
 9. The chip package with asymmetricmolding as recited in claim 1, wherein the lead frame further comprisesa plurality of bus bars and the bus bars are adjacent to the inner leadportions.
 10. The chip package with asymmetric molding as recited inclaim 9, further comprising a plurality of second bonding wireselectrically connected between the chip and the bus bars, wherein theencapsulant further encapsulates the second bonding wires and the busbars.
 11. The chip package with asymmetric molding as recited in claim1, wherein the turbulent plate has a plurality of openings.
 12. The chippackage with asymmetric molding as recited in claim 1, wherein thethickness of the encapsulant part under the bulge portion of theturbulent plate and the thickness of the encapsulant part over the bulgeportion of the turbulent plate are not equal.